What are symptoms of a tumor on the pituitary?

Depends -type? Size? Sometimes there are no symptoms especially if small and non functioning. If big - visual problems, headache. If functioning- depends on which if the many hormones the pituitary makes is over produced.
MANY. Symptoms depend on what structures the pituitary 'presses on' or what excess hormones are being produced. For example excess prolactin causes breast milk production in females or impotence in males. Also the pituitary sits on top the optic nerves so visual (fields) may be affected. A 'pituitary mri' is the best test along with lab evaluation.